Printhead nozzle arrangement with a micro-electromechanical shape memory alloy based actuator

ABSTRACT

A printhead nozzle arrangement includes a substrate. Drive circuitry is positioned on the substrate. A nozzle chamber structure is arranged on the substrate and defines a nozzle chamber in fluid communication with a supply of ink and an ink ejection port in fluid communication with the nozzle chamber. An actuator is connected to the drive circuitry and is operatively positioned with respect to the nozzle chamber. The actuator is reciprocally deformable between a quiescent condition and an active condition to eject ink from the ink ejection port. At least a portion of the actuator is in the form of a shape memory alloy which is in a pre-stressed martensitic phase when the actuator is in the quiescent condition and in an austenitic phase when the actuator is in the active condition so that cyclic phase changes generate the reciprocal movement.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a Continuation of U.S. application Ser. No.10/893,380 filed on Jul. 19, 2004, now issued U.S. Pat. No. 6,938,992,which is a Continuation of U.S. patent application Ser. No. 10/307,348filed on Dec. 2, 2002, now issued as U.S. Pat. No. 6,764,166, which is aContinuation of Ser. No. 09/113,122, filed on Jul. 10, 1998, now issuedas U.S. Pat. No. 6,557,977, the entire contents of which are hereinincorporated by reference.

The following Australian provisional patent applications are herebyincorporated by reference. For the purposes of location andidentification, US patents/patent applications identified by their USpatent/patent application serial numbers (USSN) are listed alongside theAustralian applications from which the US patents/patent applicationsclaim the right of priority.

CROSS-REFERENCED U.S. patent/patent application AUSTRALIAN (CLAIMINGRIGHT OF PROVISIONAL PRIORITY FROM PATENT AUSTRALIAN DOCKET APPLICATIONNO. PROVISIONAL APPLICATION) NO. PO7991 6,750,901 ART01 PO8505 6,476,863ART02 PO7988 6,788,336 ART03 PO9395 6,322,181 ART04 PO8017 6,597,817ART06 PO8014 6,227,648 ART07 PO8025 6,727,948 ART08 PO8032 6,690,419ART09 PO7999 6,727,951 ART10 PO7998 09/112,742 ART11 PO8031 09/112,741ART12 PO8030 6,196,541 ART13 PO7997 6,195,150 ART15 PO7979 6,362,868ART16 PO8015 09/112,738 ART17 PO7978 6831681 ART18 PO7982 6,431,669ART19 PO7989 6,362,869 ART20 PO8019 6,472,052 ART21 PO7980 6,356,715ART22 PO8018 09/112,777 ART24 PO7938 6,636,216 ART25 PO8016 6,366,693ART26 PO8024 6,329,990 ART27 PO7940 09/113,072 ART28 PO7939 6,459,495ART29 PO8501 6,137,500 ART30 PO8500 6,690,416 ART31 PO7987 09/113,071ART32 PO8022 6,398,328 ART33 PO8497 09/113,090 ART34 PO8020 6,431,704ART38 PO8023 09/113,222 ART39 PO8504 09/112,786 ART42 PO8000 6,415,054ART43 PO7977 09/112,782 ART44 PO7934 6,665,454 ART45 PO7990 6,542,645ART46 PO8499 6,486,886 ART47 PO8502 6,381,361 ART48 PO7981 6,317,192ART50 PO7986 6850274 ART51 PO7983 09/113,054 ART52 PO8026 6,646,757ART53 PO8027 09/112,759 ART54 PO8028 6,624,848 ART56 PO9394 6,357,135ART57 PO9396 09/113,107 ART58 PO9397 6,271,931 ART59 PO9398 6,353,772ART60 PO9399 6,106,147 ART61 PO9400 6,665,008 ART62 PO9401 6,304,291ART63 PO9402 09/112,788 ART64 PO9403 6,305,770 ART65 PO9405 6,289,262ART66 PP0959 6,315,200 ART68 PP1397 6,217,165 ART69 PP2370 6,786,420DOT01 PP2371 09/113,052 DOT02 PO8003 6,350,023 Fluid01 PO8005 6,318849Fluid02 PO8066 6,227,652 IJ01 PO8072 6,213,588 IJ02 PO8040 6,213,589IJ03 PO8071 6,231,163 IJ04 PO8047 6,247,795 IJ05 PO8035 6,394,581 IJ06PO8044 6,244,691 IJ07 PO8063 6,257,704 IJ08 PO8057 6,416,168 IJ09 PO80566,220,694 IJ10 PO8069 6,257,705 IJ11 PO8049 6,247,794 IJ12 PO80366,234,610 IJ13 PO8048 6,247,793 IJ14 PO8070 6,264,306 IJ15 PO80676,241,342 IJ16 PO8001 6,247,792 IJ17 PO8038 6,264,307 IJ18 PO80336,254,220 IJ19 PO8002 6,234,611 IJ20 PO8068 6,302,528 IJ21 PO80626,283.582 IJ22 PO8034 6,239,821 IJ23 PO8039 6,338,547 IJ24 PO80416,247,796 IJ25 PO8004 6,557,977 IJ26 PO8037 6,390,603 IJ27 PO80436,362,843 IJ28 PO8042 6,293,653 IJ29 PO8064 6,312,107 IJ30 PO93896,227,653 IJ31 PO9391 6,234,609 IJ32 PP0888 6,238,040 IJ33 PP08916,188,415 IJ34 PP0890 6,227,654 IJ35 PP0873 6,209,989 IJ36 PP09936,247,791 IJ37 PP0890 6,336,710 IJ38 PP1398 6,217,153 IJ39 PP25926,416,167 IJ40 PP2593 6,243,113 IJ41 PP3991 6,283,581 IJ42 PP39876,247,790 IJ43 PP3985 6,260,953 IJ44 PP3983 6,267,469 IJ45 PO79356,224,780 IJM01 PO7936 6,235,212 IJM02 PO7937 6,280,643 IJM03 PO80616,284,147 IJM04 PO8054 6,214,244 IJM05 PO8065 6,071,750 IJM06 PO80556,267,905 IJM07 PO8053 6,251,298 IJM08 PO8078 6,258,285 IJM09 PO79336,225,138 IJM10 PO7950 6,241,904 IJM11 PO7949 6,299,786 IJM12 PO806009/113,124 IJM13 PO8059 6,231,773 IJM14 PO8073 6,190,931 IJM15 PO80766,248,249 IJM16 PO8075 6,290,862 IJM17 PO8079 6,241,906 IJM18 PO80506,565,762 IJM19 PO8052 6,241,905 IJM20 PO7948 6,451,216 IJM21 PO79516,231,772 IJM22 PO8074 6,274,056 IJM23 PO7941 6,290,861 IJM24 PO80776,248,248 IJM25 PO8058 6,306,671 IJM26 PO8051 6,331,258 IJM27 PO80456,111,754 IJM28 PO7952 6,294,101 IJM29 PO8046 6,416,679 IJM30 PO93906,264,849 IJM31 PO9392 6,254,793 IJM32 PP0889 6,235,211 IJM35 PP08876,491,833 IJM36 PP0882 6,264,850 IJM37 PP0874 6,258,284 IJM38 PP13966,312,615 IJM39 PP3989 6,228,668 IJM40 PP2591 6,180,427 IJM41 PP39906,171,875 IJM42 PP3986 6,267,904 IJM43 PP3984 6,245,247 IJM44 PP39826,315,914 IJM45 PP0895 6,231,148 IR01 PP0870 09/113,106 IR02 PP08696,293,658 IR04 PP0887 6,614,560 IR05 PP0885 6,238,033 IR06 PP08846,312,070 IR10 PP0886 6,238,111 IR12 PP0871 09/113,086 IR13 PP087609/113,094 IR14 PP0877 6,378,970 IR16 PP0878 6,196,739 IR17 PP087909/112,774 IR18 PP0883 6,270,182 IR19 PP0880 6,152,619 IR20 PP088109/113,092 IR21 PO8006 6,087,638 MEMS02 PO8007 6,340,222 MEMS03 PO800809/113,062 MEMS04 PO8010 6,041,600 MEMS05 PO8011 6,299,300 MEMS06 PO79476,067,797 MEMS07 PO7944 6,286,935 MEMS09 PO7946 6,044,646 MEMS10 PO939309/113,065 MEMS11 PP0875 09/113,078 MEMS12 PP0894 6,382,769 MEMS13

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

FIELD OF THE INVENTION

The present invention relates to ink jet printing and in particulardiscloses a shape memory alloy ink jet printer.

The present invention further relates to the field of drop on demand inkjet printing.

BACKGROUND OF THE INVENTION

Many different types of printing have been invented, a large number ofwhich are presently in use. The known forms of print have a variety ofmethods for marking the print media with a relevant marking media.Commonly used forms of printing include offset printing, laser printingand copying devices, dot matrix type impact printers, thermal paperprinters, film recorders, thermal wax printers, dye sublimation printersand ink jet printers both of the drop on demand and continuous flowtype. Each type of printer has its own advantages and problems whenconsidering cost, speed, quality, reliability, simplicity ofconstruction and operation etc.

In recent years, the field of ink jet printing, wherein each individualpixel of ink is derived from one or more ink nozzles has becomeincreasingly popular primarily due to its inexpensive and versatilenature.

Many different techniques on ink jet printing have been invented. For asurvey-of the field, reference is made to an article by J Moore,“Non-Impact Printing: Introduction and Historical Perspective”, OutputHard Copy Devices, Editors R Dubeck and S Sherr, pages 207–220 (1988).

Ink Jet printers themselves come in many different types. Theutilisation of a continuous stream ink in ink jet printing appears todate back to at least 1929 wherein U.S. Pat. No. 1,941,001 by Hanselldiscloses a simple form of continuous stream electro-static ink jetprinting.

U.S. Pat. No. 3,596,275 by Sweet also discloses a process of acontinuous ink jet printing including the step wherein the ink jetstream is modulated by a high frequency electro-static field so as tocause drop separation. This technique is still utilized by severalmanufacturers including Elmjet and Scitex (see also U.S. Pat. No.3,373,437 by Sweet et al)

Piezoelectric ink jet printers are also one form of commonly utilizedink jet printing device. Piezoelectric systems are disclosed by Kyseret. al. in U.S. Pat. No. 3,946,398 (1970) which utilizes a diaphragmmode of operation, by Zolten in U.S. Pat. No. 3,683,212 (1970) whichdiscloses a squeeze mode of operation of a piezoelectric crystal, Stemmein U.S. Pat. No. 3,747,120 (1972) discloses a bend mode of piezoelectricoperation, Howkins in U.S. Pat. No. 4,459,601 discloses a piezoelectricpush mode actuation of the ink jet stream and Fischbeck in U.S. Pat. No.4,584,590 which discloses a shear mode type of piezoelectric transducerelement.

Recently, thermal ink jet printing has become an extremely popular formof ink jet printing. The ink jet printing techniques include thosedisclosed by Endo et al in GB 2007162 (1979) and Vaught et al in U.S.Pat. No. 4,490,728. Both the aforementioned references disclosed ink jetprinting techniques rely upon the activation of an electrothermalactuator which results in the creation of a bubble in a constrictedspace, such as a nozzle, which thereby causes the ejection of ink froman aperture connected to the confined space onto a relevant print media.Printing devices utilizing the electro-thermal actuator are manufacturedby manufacturers such as Canon and Hewlett Packard.

As can be seen from the foregoing, many different types of printingtechnologies are available. Ideally, a printing technology should have anumber of desirable attributes. These include inexpensive constructionand operation, high speed operation, safe and continuous long termoperation etc. Each technology may have its own advantages anddisadvantages in the areas of cost, speed, quality, reliability, powerusage, simplicity of construction operation, durability and consumables.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide for a new form ofink jet printing device that utilizes a shape memory alloy in itsactivation method.

According to a first aspect of the invention, there is provided amicro-electromechanical fluid ejection mechanism, the fluid ejectionmechanism comprising

a substrate that incorporates drive circuitry;

a nozzle chamber structure arranged on the substrate to define a nozzlechamber and a fluid ejection port in fluid communication with the nozzlechamber; and

an actuator that is fast at one end with the substrate and that extendsinto the nozzle chamber, the actuator comprising

-   -   an actuating member that is connected to the drive circuitry and        anchored at one end to the substrate, the actuating member being        displaceable between a quiescent position and an active position        to eject fluid from the ejection port, at least a portion of the        actuating member being of a shape memory alloy which is        configured so that, when the shape memory alloy makes a phase        transformation, the actuating member is displaced between the        quiescent and active positions, the actuating member being        connected to the drive circuitry so that the shape memory alloy        can be heated above its phase change temperature on receipt of        an electrical signal from the drive circuitry.

The actuating member may incorporate a heating circuit of the shapememory alloy, the heating circuit being connected to the drive circuitryof the substrate.

The actuating member may be a laminated structure, with the heatercircuit defining one layer of the actuating member.

The actuating member may include a pre-stressing layer positioned on,and mechanically fast with, the heating circuit. The shape memory alloymay have a generally planar form when in the austenitic phase and thepre-stressing layer may serve to curl the actuating member away from theejection port when the shape memory alloy is in the martensitic phasesuch that, when heated, the shape memory alloy drives the actuatingmember into a planar form, thereby ejecting a drop of ink from theejection port.

The shape memory alloy may be a nickel titanium alloy. The pre-stressinglayer may be high stress silicon nitride.

The heating circuit may be interposed between the pre-stressing layerand a stress reference layer for the pre-stressing layer.

The nozzle chamber structure may be defined by the substrate as a resultof an etching process carried out on the substrate, such that one of thelayers of the substrate defines the ejection port on one side of thesubstrate and the actuator is positioned on an opposite side of thesubstrate.

According to a second aspect of the present invention there is provideda method of ejecting ink from a chamber comprising the steps of: a)providing a cantilevered beam actuator incorporating a shape memoryalloy; and b) transforming said shape memory alloy from its martensiticphase to its austenitic phase or vice versa to cause the ink to ejectfrom said chamber. Further, the actuator comprises a conductive shapememory alloy panel in a quiescent state and which transfers to an inkejection state upon heating thereby causing said ink ejection from thechamber. Preferably, the heating occurs by means of passing a currentthrough the shape memory alloy. The chamber is formed from acrystallographic etch of a silicon wafer so as to have one surface ofthe chamber substantially formed by the actuator. Advantageously, theactuator is formed from a conductive shape memory alloy arranged in aserpentine form and is attached to one wall of the chamber opposite anozzle port from which ink is ejected. Further, the nozzle port isformed by the back etching of a silicon wafer to the epitaxial layer andetching a nozzle port hole in the epitaxial layer. The crystallographicetch includes providing side wall slots of non-etched layers of aprocessed silicon wafer so as to the extend the dimensions of thechamber as a result of the crystallographic etch process. Preferably,the shape memory alloy comprises nickel titanium alloy.

BRIEF DESCRIPTION OF THE DRAWINGS

Notwithstanding any other forms which may fall within the scope of thepresent invention, preferred forms of the invention will now bedescribed, by way of example only, with reference to the accompanyingdrawings which:

FIG. 1 is an exploded perspective view of a single ink jet nozzle asconstructed in accordance with the preferred embodiment;

FIG. 2 is a top cross sectional view of a single ink jet nozzle in itsquiescent state taken along line A—A in FIG. 1;

FIG. 3 is a top cross sectional view of a single ink jet nozzle in itsactuated state taken along line A—A in FIG. 1;

FIG. 4 provides a legend of the materials indicated in FIG. 5 to 15; and

FIG. 5 to FIG. 15 illustrate sectional views of the manufacturing stepsin one form of construction of an ink jet printhead nozzle.

DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS

In the preferred embodiment, shape memory materials are utilised toconstruct an actuator suitable for injecting ink from the nozzle of anink chamber.

Turning to FIG. 1, there is illustrated an exploded perspective view 10of a single ink jet nozzle as constructed in accordance with thepreferred embodiment. The ink jet nozzle 10 is constructed from asilicon wafer base utilizing back etching of the wafer to a boron dopedepitaxial layer. Hence, the ink jet nozzle 10 comprises a lower layer 11which is constructed from boron doped silicon. The boron doped siliconlayer is also utilized a crystallographic etch stop layer. The nextlayer comprises the silicon layer 12 that includes a crystallographicpit 13 having side walls etched at the usual angle of 54.74. The layer12 also includes the various required circuitry and transistors forexample, CMOS layer (not shown). After this, a 0.5 micron thick thermalsilicon oxide layer 15 is grown on top of the silicon wafer 12.

After this, comes various layers which can comprise a two level metalCMOS process layers which provide the metal interconnect for the CMOStransistors formed within the layer 12. The various metal pathways etc.are not shown in FIG. 1 but for two metal interconnects 18, 19 whichprovide interconnection between a shape memory alloy layer 20 and theCMOS metal layers 16. The shape memory metal layer is next and is shapedin the form of a serpentine coil to be heated by end interconnect/viaportions 21,23. A top nitride layer 22 is provided for overallpassivation and protection of lower layers in addition to providing ameans of inducing tensile stress to curl upwards the shape memory alloylayer 20 in its quiescent state.

The preferred embodiment relies upon the thermal transition of a shapememory alloy 20 (SMA) from its martensitic phase to its austeniticphase. The basis of a shape memory effect is a martensitictransformation which creates a polydemane phase upon cooling. Thispolydemane phase accommodates finite reversible mechanical deformationswithout significant changes in the mechanical self energy of the system.Hence, upon re-transformation to the austenitic state the system returnsto its former macroscopic state to displaying the well known mechanicalmemory. The thermal transition is achieved by passing an electricalcurrent through the SMA. The actuator layer 20 is suspended at theentrance to a nozzle chamber connected via leads 18, 19 to the lowerlayers.

In FIG. 2, there is shown a cross-section of a single nozzle 10 when inits quiescent state, the section basically being taken through the lineA—A of FIG. 1. The actuator 30 is bent away from the nozzle when in itsquiescent state. In FIG. 3, there is shown a corresponding cross-sectionfor a single nozzle 10 when in an actuated state. When energized, theactuator 30 straightens, with the corresponding result that the ink ispushed out of the nozzle. The process of energizing the actuator 30requires supplying enough energy to raise the SMA above its transitiontemperature, and to provide the latent heat of transformation to the SMA20.

Obviously, the SMA martensitic phase must be pre-stressed to achieve adifferent shape from the austenitic phase. For printheads with manythousands of nozzles, it is important to achieve this pre-stressing in abulk manner. This is achieved by depositing the layer of silicon nitride22 using Plasma Enhanced Chemical Vapour Deposition (PECVD) at around300° C. over the SMA layer. The deposition occurs while the SMA is inthe austenitic shape. After the printhead cools to room temperature thesubstrate under the SMA bend actuator is removed by chemical etching ofa sacrificial substance. The silicon nitride layer 22 is under tensilestress, and causes the actuator to curl upwards. The weak martensiticphase of the SMA provides little resistance to this curl. When the SMAis heated to its austenitic phase, it returns to the flat shape intowhich it was annealed during the nitride deposition. The transformationbeing rapid enough to result in the ejection of ink from the nozzlechamber.

There is one SMA bend actuator 30 for each nozzle. One end 31 of the SMAbend actuator is mechanically connected to the substrate. The other endis free to move under the stresses inherent in the layers.

Returning to FIG. 1 the actuator layer is therefore composed of threelayers:

1. An SiO₂ lower layer 15. This layer acts as a stress ‘reference’ forthe nitride tensile layer. It also protects the SMA from thecrystallographic silicon etch that forms the nozzle chamber. This layercan be formed as part of the standard CMOS process for the activeelectronics of the printhead.

2. A SMA heater layer 20. A SMA such as nickel titanium (NiTi) alloy isdeposited and etched into a serpentine form to increase the electricalresistance.

3. A silicon nitride top layer 22. This is a thin layer of highstiffness which is deposited using PECVD. The nitride stoichiometry isadjusted to achieve a layer with significant tensile stress at roomtemperature relative to the SiO₂ lower layer. Its purpose is to bend theactuator at the low temperature martensitic phase.

As noted previously the ink jet nozzle of FIG. 1 can be constructed byutilizing a silicon wafer having a buried boron epitaxial layer. The 0.5micron thick dioxide layer 15 is then formed having side slots 45 whichare utilized in a subsequent crystallographic etch. Next, the variousCMOS layers 16 are formed including drive and control circuitry (notshown). The SMA layer 20 is then created on top of layers 15/16 andbeing interconnected with the drive circuitry. Subsequently, a siliconnitride layer 22 is formed on top. Each of the layers 15, 16, 22 includethe various slots eg. 45 which are utilized in a subsequentcrystallographic etch. The silicon wafer is subsequently thinned bymeans of back etching with the etch stop being the boron layer 11.Subsequent boron etching forms the nozzle hole eg. 47 and rim 46 (FIG.3). Subsequently, the chamber proper is formed by means of acrystallographic etch with the slots 45 defining the extent of the etchwithin the silicon oxide layer 12.

A large array of nozzles can be formed on the same wafer which in turnis attached to an ink chamber for filling the nozzle chambers.

One form of detailed manufacturing process which can be used tofabricate monolithic ink jet printheads operating in accordance with theprinciples taught by the present embodiment can proceed utilizing thefollowing steps:

1. Using a double sided polished wafer deposit 3 microns of epitaxialsilicon heavily doped with boron.

2. Deposit 10 microns of epitaxial silicon, either p-type or n-type,depending upon the CMOS process used.

3. Complete drive transistors, data distribution, and timing circuitsusing a 0.5 micron, one poly, 2 metal CMOS process. This step is shownin FIG. 5. For clarity, these diagrams may not be to scale, and may notrepresent a cross section though any single plane of the nozzle. FIG. 4is a key to representations of various materials in these manufacturingdiagrams, and those of other cross referenced ink jet configurations.

4. Etch the CMOS oxide layers down to silicon or aluminum using Mask 1.This mask defines the nozzle chamber, and the edges of the printheadschips. This step is shown in FIG. 6.

5. Crystallographically etch the exposed silicon using, for example, KOHor EDP (ethylenediamine pyrocatechol). This etch stops on <111>crystallographic planes, and on the boron doped silicon buried layer.This step is shown in FIG. 7.

6. Deposit 12 microns of sacrificial material. Planarize down to oxideusing CMP. The sacrificial material temporarily fills the nozzle cavity.This step is shown in FIG. 8.

7. Deposit 0.1 microns of high stress silicon nitride (Si3N4).

8. Etch the nitride layer using Mask 2. This mask defines the contactvias from the shape memory heater to the second-level metal contacts.

9. Deposit a seed layer.

10. Spin on 2 microns of resist, expose with Mask 3, and develop. Thismask defines the shape memory wire embedded in the paddle. The resistacts as an electroplating mold. This step is shown in FIG. 9.

11. Electroplate 1 micron of Nitinol. Nitinol is a ‘shape memory’ alloyof nickel and titanium, developed at the Naval Ordnance Laboratory inthe US (hence Ni—Ti—NOL). A shape memory alloy can be thermally switchedbetween its weak martensitic state and its high stiffness austenicstate.

12. Strip the resist and etch the exposed seed layer. This step is shownin FIG. 10.

13. Wafer probe. All electrical connections are complete at this point,bond pads are accessible, and the chips are not yet separated.

14. Deposit 0.1 microns of high stress silicon nitride. High stressnitride is used so that once the sacrificial material is etched, and thepaddle is released, the stress in the nitride layer will bend therelatively weak martensitic phase of the shape memory alloy. As theshape memory alloy—in its austenic phase—is flat when it is annealed bythe relatively high temperature deposition of this silicon nitridelayer, it will return to this flat state when electrothermally heated.

15. Mount the wafer on a glass blank and back-etch the wafer using KOHwith no mask. This etch thins the wafer and stops at the buried borondoped silicon layer. This step is shown in FIG. 11.

16. Plasma back-etch the boron doped silicon layer to a depth of 1micron using Mask 4. This mask defines the nozzle rim. This step isshown in FIG. 12.

17. Plasma back-etch through the boron doped layer using Mask 5. Thismask defines the nozzle, and the edge of the chips. At this stage, thechips are still mounted on the glass blank. This step is shown in FIG.13.

18. Strip the adhesive layer to detach the chips from the glass blank.Etch the sacrificial layer. This process completely separates the chips.This step is shown in FIG. 14.

19. Mount the printheads in their packaging, which may be a moldedplastic former incorporating ink channels which supply different colorsof ink to the appropriate regions of the front surface of the wafer.

20. Connect the printheads to their interconnect systems.

21. Hydrophobize the front surface of the printheads.

22. Fill with ink and test the completed printheads. A filled nozzle isshown in FIG. 15.

It would be appreciated by a person skilled in the art that numerousvariations and/or modifications may be made to the present invention asshown in the specific embodiment without departing from the spirit orscope of the invention as broadly described. The present embodiment is,therefore, to be considered in all respects to be illustrative and notrestrictive.

The presently disclosed ink jet printing technology is potentiallysuited to a wide range of printing systems including: color andmonochrome office printers, short run digital printers, high speeddigital printers, offset press supplemental printers, low cost scanningprinters, high speed pagewidth printers, notebook computers with inbuiltpagewidth printers, portable color and monochrome printers, color andmonochrome copiers, color and monochrome facsimile machines, combinedprinter, facsimile and copying machines, label printers, large formatplotters, photograph copiers, printers for digital photographic‘minilabs’, video printers, PHOTO CD (PHOTO CD is a registered trademarkof the Eastman Kodak Company) printers, portable printers for PDAs,wallpaper printers, indoor sign printers, billboard printers, fabricprinters, camera printers and fault tolerant commercial printer arrays.

Ink Jet Technologies

The embodiments of the invention use an ink jet printer type device. Ofcourse many different devices could be used. However presently popularink jet printing technologies are unlikely to be suitable.

The most significant problem with thermal ink jet is power consumption.This is approximately 100 times that required for high speed, and stemsfrom the energy-inefficient means of drop ejection. This involves therapid boiling of water to produce a vapor bubble which expels the ink.Water has a very high heat capacity, and must be superheated in thermalink jet applications. This leads to an efficiency of around 0.02%, fromelectricity input to drop momentum (and increased surface area) out.

The most significant problem with piezoelectric ink jet is size andcost. Piezoelectric crystals have a very small deflection at reasonabledrive voltages, and therefore require a large area for each nozzle.Also, each piezoelectric actuator must be connected to its drive circuiton a separate substrate. This is not a significant problem at thecurrent limit of around 300 nozzles per printhead, but is a majorimpediment to the fabrication of pagewidth printheads with 19,200nozzles.

Ideally, the ink jet technologies used meet the stringent requirementsof in-camera digital color printing and other high quality, high speed,low cost printing applications. To meet the requirements of digitalphotography, new ink jet technologies have been created. The targetfeatures include:

low power (less than 10 Watts)

high resolution capability (1,600 dpi or more)

photographic quality output

low manufacturing cost

small size (pagewidth times minimum cross section)

high speed (<2 seconds per page).

All of these features can be met or exceeded by the ink jet systemsdescribed below with differing levels of difficulty. Forty-fivedifferent ink jet technologies have been developed by the Assignee togive a wide range of choices for high volume manufacture. Thesetechnologies form part of separate applications assigned to the presentAssignee as set out in the table under the heading Cross References toRelated Applications.

The ink jet designs shown here are suitable for a wide range of digitalprinting systems, from battery powered one-time use digital cameras,through to desktop and network printers, and through to commercialprinting systems.

For ease of manufacture using standard process equipment, the printheadis designed to be a monolithic 0.5 micron CMOS chip with MEMS postprocessing. For color photographic applications, the printhead is 100 mmlong, with a width which depends upon the ink jet type. The smallestprinthead designed is IJ38, which is 0.35 mm wide, giving a chip area of35 square mm. The printheads each contain 19,200 nozzles plus data andcontrol circuitry.

Ink is supplied to the back of the print head by injection moldedplastic ink channels. The molding requires 50 micron features, which canbe created using a lithographically micromachined insert in a standardinjection molding tool. Ink flows through holes etched through the waferto the nozzle chambers fabricated on the front surface of the wafer. Theprinthead is connected to the camera circuitry by tape automatedbonding.

Tables of Drop-on-Demand Ink Jets

Eleven important characteristics of the fundamental operation ofindividual inkjet nozzles have been identified. These characteristicsare largely orthogonal, and so can be elucidated as an elevendimensional matrix. Most of the eleven axes of this matrix includeentries developed by the present assignee.

The following tables form the axes of an eleven dimensional table of inkjet types.

Actuator mechanism (18 types)

Basic operation mode (7 types)

Auxiliary mechanism (8 types)

Actuator amplification or modification method (17 types)

Actuator motion (19 types)

Nozzle refill method (4 types)

Method of restricting back-flow through inlet (10 types)

Nozzle clearing method (9 types)

Nozzle plate construction (9 types)

Drop ejection direction (5 types)

Ink type (7 types)

The complete eleven dimensional table represented by these axes contains36.9 billion possible configurations of ink jet nozzle. While not all ofthe possible combinations result in a viable ink jet technology, manymillion configurations are viable. It is clearly impractical toelucidate all of the possible configurations. Instead, certain ink jettypes have been investigated in detail. These are designated IJ01 toIJ45 which match the docket numbers in the table under the heading CrossReferenced to Related Application.

Other ink jet configurations can readily be derived from theseforty-five examples by substituting alternative configurations along oneor more of the 11 axes. Most of the IJ01 to IJ45 examples can be madeinto ink jet printheads with characteristics superior to any currentlyavailable ink jet technology.

Where there are prior art examples known to the inventor, one or more ofthese examples are listed in the examples column of the tables below.The IJ01 to IJ45 series are also listed in the examples column. In somecases, a print technology may be listed more than once in a table, whereit shares characteristics with more than one entry.

Suitable applications for the ink jet technologies include: Homeprinters, Office network printers, Short run digital printers,Commercial print systems, Fabric printers, Pocket printers, Internet WWWprinters, Video printers, Medical imaging, Wide format printers,Notebook PC printers, Fax machines, Industrial printing systems,Photocopiers, Photographic minilabs etc.

The information associated with the aforementioned 11 dimensional matrixare set out in the following tables.

Description Advantages Disadvantages Examples ACTUATOR MECHANISM(APPLIED ONLY TO SELECTED INK DROPS) Thermal An electrothermal Largeforce High power Canon Bubblejet bubble heater heats the ink togenerated Ink carrier 1979 Endo et al GB above boiling point, Simplelimited to water patent 2,007,162 transferring significant constructionLow efficiency Xerox heater-in- heat to the aqueous No moving parts Highpit 1990 Hawkins et ink. A bubble Fast operation temperatures al U.S.Pat. No. 4,899,181 nucleates and quickly Small chip area requiredHewlett-Packard forms, expelling the required for actuator Highmechanical TIJ 1982 Vaught et ink. stress al U.S. Pat. No. 4,490,728 Theefficiency of the Unusual process is low, with materials requiredtypically less than Large drive 0.05% of the electrical transistorsenergy being Cavitation causes transformed into actuator failure kineticenergy of the Kogation reduces drop. bubble formation Large print headsare difficult to fabricate Piezoelectric A piezoelectric crystal Lowpower Very large area Kyser et al U.S. Pat. No. such as lead consumptionrequired for actuator 3,946,398 lanthanum zirconate Many ink typesDifficult to Zoltan U.S. Pat. No. (PZT) is electrically can be usedintegrate with 3,683,212 activated, and either Fast operationelectronics 1973 Stemme expands, shears, or High efficiency High voltageU.S. Pat. No. 3,747,120 bends to apply drive transistors Epson Styluspressure to the ink, required Tektronix ejecting drops. Full pagewidthIJ04 print heads impractical due to actuator size Requires electricalpoling in high field strengths during manufacture Electrostrictive Anelectric field is Low power Low maximum Seiko Epson, used to activateconsumption strain (approx. Usui et all JP electrostriction in Many inktypes 0.01%) 253401/96 relaxor materials such can be used Large areaIJ04 as lead lanthanum Low thermal required for actuator zirconatetitanate expansion due to low strain (PLZT) or lead Electric fieldResponse speed magnesium niobate strength required is marginal (~10 μs)(PMN). (approx. 3.5 V/μm) High voltage can be generated drivetransistors without difficulty required Does not require Full pagewidthelectrical poling print heads impractical due to actuator sizeFerroelectric An electric field is Low power Difficult to IJ04 used toinduce a phase consumption integrate with transition between the Manyink types electronics antiferroelectric (AFE) can be used Unusual andferroelectric (FE) Fast operation materials such as phase. Perovskite(<1 μs) PLZSnT are materials such as tin Relatively high requiredmodified lead longitudinal strain Actuators require lanthanum zirconateHigh efficiency a large area titanate (PLZSnT) Electric field exhibitlarge strains of strength of around 3 V/μm up to 1% associated can bereadily with the AFE to FE provided phase transition. ElectrostaticConductive plates are Low power Difficult to IJ02, IJ04 plates separatedby a consumption operate electrostatic compressible or fluid Many inktypes devices in an dielectric (usually air). can be used aqueous Uponapplication of a Fast operation environment voltage, the plates Theelectrostatic attract each other and actuator will displace ink, causingnormally need to be drop ejection. The separated from the conductiveplates may ink be in a comb or Very large area honeycomb structure,required to achieve or stacked to increase high forces the surface areaand High voltage therefore the force. drive transistors may be requiredFull pagewidth print heads are not competitive due to actuator sizeElectrostatic A strong electric field Low current High voltage 1989Saito et al, pull is applied to the ink, consumption required U.S. Pat.No. 4,799,068 on ink whereupon Low temperature May be damaged 1989 Miuraet al, electrostatic attraction by sparks due to air U.S. Pat. No.4,810,954 accelerates the ink breakdown Tone-jet towards the printRequired field medium. strength increases as the drop size decreasesHigh voltage drive transistors required Electrostatic field attractsdust Permanent An electromagnet Low power Complex IJ07, IJ10 magnetdirectly attracts a consumption fabrication electromagnetic permanentmagnet, Many ink types Permanent displacing ink and can be used magneticmaterial causing drop ejection. Fast operation such as Neodymium Rareearth magnets High efficiency Iron Boron (NdFeB) with a field strengthEasy extension required. around 1 Tesla can be from single nozzles Highlocal used. Examples are: to pagewidth print currents required SamariumCobalt heads Copper (SaCo) and magnetic metalization should materials inthe be used for long neodymium iron boron electromigration family(NdFeB, lifetime and low NdDyFeBNb, resistivity NdDyFeB, etc) Pigmentedinks are usually infeasible Operating temperature limited to the Curietemperature (around 540 K) Soft A solenoid induced a Low power ComplexIJ01, IJ05, IJ08, magnetic magnetic field in a soft consumptionfabrication IJ10, IJ12, IJ14, core electromagnetic magnetic core or yokeMany ink types Materials not IJ15, IJ17 fabricated from a can be usedusually present in a ferrous material such Fast operation CMOS fab suchas as electroplated iron High efficiency NiFe, CoNiFe, or alloys such asCoNiFe Easy extension CoFe are required [1], CoFe, or NiFe from singlenozzles High local alloys. Typically, the to pagewidth print currentsrequired soft magnetic material heads Copper is in two parts, whichmetalization should are normally held be used for long apart by aspring. electromigration When the solenoid is lifetime and low actuated,the two parts resistivity attract, displacing the Electroplating is ink.required High saturation flux density is required (2.0–2.1 T isachievable with CoNiFe [1]) Lorenz The Lorenz force Low power Force actsas a IJ06, IJ11, IJ13, force acting on a current consumption twistingmotion IJ16 carrying wire in a Many ink types Typically, only a magneticfield is can be used quarter of the utilized. Fast operation solenoidlength This allows the High efficiency provides force in a magneticfield to be Easy extension useful direction supplied externally to fromsingle nozzles High local the print head, for to pagewidth printcurrents required example with rare heads Copper earth permanentmetalization should magnets. be used for long Only the currentelectromigration carrying wire need be lifetime and low fabricated onthe print- resistivity head, simplifying Pigmented inks materials areusually requirements. infeasible Magnetostriction The actuator uses theMany ink types Force acts as a Fischenbeck, giant magnetostrictive canbe used twisting motion U.S. Pat. No. 4,032,929 effect of materials Fastoperation Unusual IJ25 such as Terfenol-D (an Easy extension materialssuch as alloy of terbium, from single nozzles Terfenol-D are dysprosiumand iron to pagewidth print required developed at the Naval heads Highlocal Ordnance Laboratory, High force is currents required henceTer-Fe-NOL). available Copper For best efficiency, the metalizationshould actuator should be pre- be used for long stressed to approx. 8MPa. electromigration lifetime and low resistivity Pre-stressing may berequired Surface Ink under positive Low power Requires Silverbrook, EPtension pressure is held in a consumption supplementary force 0771 658A2 and reduction nozzle by surface Simple to effect drop related patenttension. The surface construction separation applications tension of theink is No unusual Requires special reduced below the materials requiredin ink surfactants bubble threshold, fabrication Speed may be causingthe ink to High efficiency limited by surfactant egress from the Easyextension properties nozzle. from single nozzles to pagewidth printheads Viscosity The ink viscosity is Simple Requires Silverbrook, EPreduction locally reduced to construction supplementary force 0771 658A2 and select which drops are No unusual to effect drop related patentto be ejected. A materials required in separation applications viscosityreduction can fabrication Requires special be achieved Easy extensionink viscosity electrothermally with from single nozzles properties mostinks, but special to pagewidth print High speed is inks can beengineered heads difficult to achieve for a 100:1 viscosity Requiresreduction. oscillating ink pressure A high temperature difference(typically 80 degrees) is required Acoustic An acoustic wave is Canoperate Complex drive 1993 Hadimioglu generated and without a nozzlecircuitry et al, EUP 550,192 focussed upon the plate Complex 1993 Elrodet al, drop ejection region. fabrication EUP 572,220 Low efficiency Poorcontrol of drop position Poor control of drop volume Thermoelastic Anactuator which Low power Efficient aqueous IJ03, IJ09, IJ17, bend reliesupon differential consumption operation requires a IJ18, IJ19, IJ20,actuator thermal expansion Many ink types thermal insulator on IJ21,IJ22, IJ23, upon Joule heating is can be used the hot side IJ24, IJ27,IJ28, used. Simple planar Corrosion IJ29, IJ30, IJ31, fabricationprevention can be IJ32, IJ33, IJ34, Small chip area difficult IJ35,IJ36, IJ37, required for each Pigmented inks IJ38, IJ39, IJ40, actuatormay be infeasible, IJ41 Fast operation as pigment particles Highefficiency may jam the bend CMOS actuator compatible voltages andcurrents Standard MEMS processes can be used Easy extension from singlenozzles to pagewidth print heads High CTE A material with a very Highforce can Requires special IJ09, IJ17, IJ18, thermoelastic highcoefficient of be generated material (e.g. PTFE) IJ20, IJ21, IJ22,actuator thermal expansion Three methods of Requires a PTFE IJ23, IJ24,IJ27, (CTE) such as PTFE deposition are deposition process, IJ28, IJ29,IJ30, polytetrafluoroethylene under development: which is not yet IJ31,IJ42, IJ43, (PTFE) is used. As chemical vapor standard in ULSI IJ44 highCTE materials deposition (CVD), fabs are usually non- spin coating, andPTFE deposition conductive, a heater evaporation cannot be followedfabricated from a PTFE is a with high conductive material is candidatefor low temperature (above incorporated. A 50 μm dielectric constant350° C.) processing long PTFE bend insulation in ULSI Pigmented inksactuator with Very low power may be infeasible, polysilicon heater andconsumption as pigment particles 15 mW power input Many ink types mayjam the bend can provide 180 μN can be used actuator force and 10 μmSimple planar deflection. Actuator fabrication motions include: Smallchip area Bend required for each Push actuator Buckle Fast operationRotate High efficiency CMOS compatible voltages and currents Easyextension from single nozzles to pagewidth print heads Conductive Apolymer with a high High force can Requires special IJ24 polymercoefficient of thermal be generated materials thermoelastic expansion(such as Very low power development (High actuator PTFE) is doped withconsumption CTE conductive conducting substances Many ink types polymer)to increase its can be used Requires a PTFE conductivity to about 3Simple planar deposition process, orders of magnitude fabrication whichis not yet below that of copper. Small chip area standard in ULSI Theconducting required for each fabs polymer expands actuator PTFEdeposition when resistively Fast operation cannot be followed heated.High efficiency with high Examples of CMOS temperature (above conductingdopants compatible voltages 350° C.) processing include: and currentsEvaporation and Carbon nanotubes Easy extension CVD deposition Metalfibers from single nozzles techniques cannot Conductive polymers topagewidth print be used such as doped heads Pigmented inks polythiophenemay be infeasible, Carbon granules as pigment particles may jam the bendactuator Shape A shape memory alloy High force is Fatigue limits IJ26memory such as TiNi (also available (stresses maximum number alloy knownas Nitinol - of hundreds of MPa) of cycles Nickel Titanium alloy Largestrain is Low strain (1%) developed at the Naval available (more than isrequired to extend Ordnance Laboratory) 3%) fatigue resistance isthermally switched High corrosion Cycle rate between its weak resistancelimited by heat martensitic state and Simple removal its high stiffnessconstruction Requires unusual austenic state. The Easy extensionmaterials (TiNi) shape of the actuator from single nozzles The latentheat of in its martensitic state to pagewidth print transformation mustis deformed relative to heads be provided the austenic shape. Lowvoltage High current The shape change operation operation causesejection of a Requires pre- drop. stressing to distort the martensiticstate Linear Linear magnetic Linear Magnetic Requires unusual IJ12Magnetic actuators include the actuators can be semiconductor ActuatorLinear Induction constructed with materials such as Actuator (LIA),Linear high thrust, long soft magnetic alloys Permanent Magnet travel,and high (e.g. CoNiFe) Synchronous Actuator efficiency using Somevarieties (LPMSA), Linear planar also require Reluctance semiconductorpermanent magnetic Synchronous Actuator fabrication materials such as(LRSA), Linear techniques Neodymium iron Switched Reluctance Longactuator boron (NdFeB) Actuator (LSRA), and travel is available Requiresthe Linear Stepper Medium force is complex multiphase Actuator (LSA).available drive circuitry Low voltage High current operation operationBASIC OPERATION MODE Actuator This is the simplest Simple operation Droprepetition Thermal ink jet directly mode of operation: the No externalrate is usually Piezoelectric ink pushes ink actuator directly fieldsrequired limited to around 10 kHz. jet supplies sufficient Satellitedrops However, this IJ01, IJ02, IJ03, kinetic energy to expel can beavoided if is not fundamental IJ04, 1105, IJ06, the drop. The drop dropvelocity is less to the method, but is IJ07, IJ09, IJ11, must have asufficient than 4 m/s related to the refill IJ12, IJ14, IJ16, velocityto overcome Can be efficient, method normally IJ20, IJ22, IJ23, thesurface tension. depending upon the used IJ24, IJ25, IJ26, actuator usedAll of the drop IJ27, IJ28, IJ29, kinetic energy must IJ30, IJ31, IJ32,be provided by the IJ33, IJ34, IJ35, actuator IJ36, IJ37, IJ38,Satellite drops IJ39, IJ40, IJ41, usually form if drop IJ42, IJ43, IJ44velocity is greater than 4.5 m/s Proximity The drops to be Very simpleprint Requires close Silverbrook, EP printed are selected by headfabrication can proximity between 0771 658 A2 and some manner (e.g. beused the print head and related patent thermally induced The drop theprint media or applications surface tension selection means transferroller reduction of does not need to May require two pressurized ink).provide the energy print heads printing Selected drops are required toseparate alternate rows of the Separated from the ink the drop from theimage in the nozzle by nozzle Monolithic color contact with the printprint heads are medium or a transfer difficult roller. Electrostatic Thedrops to be Very simple print Requires very Silverbrook, EP pull printedare selected by head fabrication can high electrostatic 0771 658 A2 andon ink some manner (e.g. be used field related patent thermally inducedThe drop Electrostatic field applications surface tension selectionmeans for small nozzle Tone-Jet reduction of does not need to sizes isabove air pressurized ink). provide the energy breakdown Selected dropsare required to separate Electrostatic field separated from the ink thedrop from the may attract dust in the nozzle by a nozzle strong electricfield. Magnetic The drops to be Very simple print Requires Silverbrook,EP pull on ink printed are selected by head fabrication can magnetic ink0771 658 A2 and some manner (e.g. be used Ink colors other relatedpatent thermally induced The drop than black are applications surfacetension selection means difficult reduction of does not need to Requiresvery pressurized ink). provide the energy high magnetic fields Selecteddrops are required to separate separated from the ink the drop from thein the nozzle by a nozzle strong magnetic field acting on the magneticink. Shutter The actuator moves a High speed (>50 kHz) Moving parts areIJ13, IJ17, IJ21 shutter to block ink operation can required flow to thenozzle. The be achieved due to Requires ink ink pressure is pulsedreduced refill time pressure modulator at a multiple of the Drop timingcan Friction and wear drop ejection be very accurate must be consideredfrequency. The actuator Stiction is energy can be very possible lowShuttered The actuator moves a Actuators with Moving parts are IJ08,IJ15, IJ18, grill shutter to block ink small travel can be required IJ19flow through a grill to used Requires ink the nozzle. The shutterActuators with pressure modulator movement need only small force can beFriction and wear be equal to the width used must be considered of thegrill holes. High speed (>50 kHz) Stiction is operation can possible beachieved Pulsed A pulsed magnetic Extremely low Requires an IJ10magnetic field attracts an ‘ink energy operation is external pulsed pullon ink pusher’ at the drop possible magnetic field pusher ejectionfrequency. An No heat Requires special actuator controls a dissipationmaterials for both catch, which prevents problems the actuator and thethe ink pusher from ink pusher moving when a drop is Complex not to beejected. construction AUXILIARY MECHANISM (APPLIED TO ALL NOZZLES) NoneThe actuator directly Simplicity of Drop ejection Most ink jets, firesthe ink drop, and construction energy must be including there is noexternal Simplicity of supplied by piezoelectric and field or otheroperation individual nozzle thermal bubble. mechanism required. Smallphysical actuator IJ01, IJ02, IJ03, size IJ04, IJ05, IJ07, IJ09, IJ11,IJ12, IJ14, IJ20, IJ22, IJ23, IJ24, IJ25, IJ26, IJ27, IJ28, IJ29, IJ30,IJ31, IJ32, IJ33, IJ34, IJ35, IJ36, IJ37, IJ38, IJ39, IJ40, IJ41, IJ42,IJ43, IJ44 Oscillating The ink pressure Oscillating ink Requiresexternal Silverbrook, EP ink pressure oscillates, providing pressure canprovide ink pressure 0771 658 A2 and (including much of the drop arefill pulse, oscillator related patent acoustic ejection energy. Theallowing higher Ink pressure applications stimulation) actuator selectswhich operating speed phase and amplitude IJ08, IJ13, IJ15, drops are tobe fired The actuators must be carefully IJ17, IJ18, IJ19, byselectively may operate with controlled IJ21 blocking or enabling muchlower energy Acoustic nozzles. The ink Acoustic lenses reflections inthe ink pressure oscillation can be used to focus chamber must be may beachieved by the sound on the designed for vibrating the print nozzleshead, or preferably by an actuator in the ink supply. Media The printhead is Low power Precision Silverbrook, EP proximity placed in closeHigh accuracy assembly required 0771 658 A2 and proximity to the printSimple print head Paper fibers may related patent medium. Selectedconstruction cause problems applications drops protrude from Cannotprint on the print head further rough substrates than unselected drops,and contact the print medium. The drop soaks into the medium fast enoughto cause drop separation. Transfer Drops are printed to a High accuracyBulky Silverbrook, EP roller transfer roller instead Wide range ofExpensive 0771 658 A2 and of straight to the print print substrates canComplex related patent medium. A transfer be used constructionapplications roller can also be used Ink can be dried Tektronix hot forproximity drop on the transfer roller melt piezoelectric separation. inkjet Any of the IJ series Electrostatic An electric field is Low powerField strength Silverbrook, EP used to accelerate Simple print headrequired for 0771 658 A2 and selected drops towards constructionseparation of small related patent the print medium. drops is near orapplications above air Tone-Jet breakdown Direct A magnetic field is Lowpower Requires Silverbrook, EP magnetic used to accelerate Simple printhead magnetic ink 0771 658 A2 and field selected drops of constructionRequires strong related patent magnetic ink towards magnetic fieldapplications the print medium. Cross The print head is Does not requireRequires external IJ06, IJ16 magnetic placed in a constant magneticmaterials magnet field magnetic field. The to be integrated in Currentdensities Lorenz force in a the print head may be high, current carryingwire manufacturing resulting in is used to move the processelectromigration actuator. problems Pulsed A pulsed magnetic Very lowpower Complex print IJ10 magnetic field is used to operation is possiblehead construction field cyclically attract a Small print head Magneticpaddle, which pushes size materials required in on the ink. A smallprint head actuator moves a catch, which selectively prevents the paddlefrom moving. ACTUATOR AMPLIFICATION OR MODIFICATION METHOD None Noactuator Operational Many actuator Thermal Bubble mechanical simplicitymechanisms have Ink jet amplification is used. insufficient travel,IJ01, IJ02, IJ06, The actuator directly or insufficient force, IJ07,IJ16, IJ25, drives the drop to efficiently drive IJ26 ejection process.the drop ejection process Differential An actuator material Providesgreater High stresses are Piezoelectric expansion expands more on onetravel in a reduced involved IJ03, IJ09, IJ17, bend side than on theother. print head area Care must be IJ18, IJ19, IJ20, actuator Theexpansion may be taken that the IJ21, IJ22, IJ23, thermal,piezoelectric, materials do not IJ24, IJ27, IJ29, magnetostrictive, ordelaminate IJ30, IJ31, IJ32, other mechanism. The Residual bend IJ33,IJ34, IJ35, bend actuator converts resulting from high IJ36, IJ37, IJ38,a high force low travel temperature or high IJ39, IJ42, IJ43, actuatormechanism to stress during IJ44 high travel, lower formation forcemechanism. Transient A trilayer bend Very good High stresses are IJ40,IJ41 bend actuator where the two temperature stability involved actuatoroutside layers are High speed, as a Care must be identical. This cancelsnew drop can be taken that the bend due to ambient fired before heatmaterials do not temperature and dissipates delaminate residual stress.The Cancels residual actuator only responds stress of formation totransient heating of one side or the other. Reverse The actuator loads aBetter coupling Fabrication IJ05, IJ11 spring spring. When the to theink complexity actuator is turned off, High stress in the the springreleases. spring This can reverse the force/distance curve of theactuator to make it compatible with the force/time requirements of thedrop ejection. Actuator A series of thin Increased travel Increased Somestack actuators are stacked. Reduced drive fabrication piezoelectric inkjets This can be voltage complexity IJ04 appropriate where Increasedactuators require high possibility of short electric field strength,circuits due to such as electrostatic pinholes and piezoelectricactuators. Multiple Multiple smaller Increases the Actuator forces IJ12,IJ13, IJ18, actuators actuators are used force available from may notadd IJ20, IJ22, IJ28, simultaneously to an actuator linearly, reducingIJ42, IJ43 move the ink. Each Multiple efficiency actuator need provideactuators can be only a portion of the positioned to control forcerequired. ink flow accurately Linear A linear spring is used Matches lowRequires print IJ15 Spring to transform a motion travel actuator withhead area for the with small travel and higher travel spring high forceinto a requirements longer travel, lower Non-contact force motion.method of motion transformation Coiled A bend actuator is Increasestravel Generally IJ17, IJ21, IJ34, actuator coiled to provide Reduceschip restricted to planar IJ35 greater travel in a area implementationsreduced chip area. Planar due to extreme implementations are fabricationdifficulty relatively easy to in other orientations. fabricate. FlexureA bend actuator has a Simple means of Care must be IJ10, IJ19, IJ33 bendsmall region near the increasing travel of taken not to exceed actuatorfixture point, which a bend actuator the elastic limit in flexes muchmore the flexure area readily than the Stress remainder of thedistribution is very actuator. The actuator uneven flexing iseffectively Difficult to converted from an accurately model even coilingto an with finite element angular bend, resulting analysis in greatertravel of the actuator tip. Catch The actuator controls a Very lowComplex IJ10 small catch. The catch actuator energy construction eitherenables or Very small Requires external disables movement of actuatorsize force an ink pusher that is Unsuitable for controlled in a bulkpigmented inks manner. Gears Gears can be used to Low force, low Movingparts are IJ13 increase travel at the travel actuators can requiredexpense of duration. be used Several actuator Circular gears, rack Canbe fabricated cycles are required and pinion, ratchets, using standardMore complex and other gearing surface MEMS drive electronics methodscan be used. processes Complex construction Friction, friction, and wearare possible Buckle plate A buckle plate can be Very fast Must staywithin S. Hirata et al, used to change a slow movement elastic limits ofthe “An Ink-jet Head actuator into a fast achievable materials for longUsing Diaphragm motion. It can also device life Microactuator”, converta high force, High stresses Proc. IEEE MEMS, low travel actuatorinvolved Feb. 1996, pp 418–423. into a high travel, Generally high IJ18,IJ27 medium force motion. power requirement Tapered A tapered magneticLinearizes the Complex IJ14 magnetic pole can increase magneticconstruction pole travel at the expense force/distance curve of force.Lever A lever and fulcrum is Matches low High stress IJ32, IJ36, IJ37used to transform a travel actuator with around the fulcrum motion withsmall higher travel travel and high force requirements into a motionwith Fulcrum area has longer travel and no linear movement, lower force.The lever and can be used for can also reverse the a fluid sealdirection of travel. Rotary The actuator is High mechanical Complex IJ28impeller connected to a rotary advantage construction impeller. A smallThe ratio of force Unsuitable for angular deflection of to travel of thepigmented inks the actuator results in actuator can be a rotation of thematched to the impeller vanes, which nozzle requirements push the inkagainst by varying the stationary vanes and number of impeller out ofthe nozzle. vanes Acoustic A refractive or No moving parts Large area1993 Hadimioglu lens diffractive (e.g. zone required et al, EUP 550,192plate) acoustic lens is Only relevant for 1993 Elrod et al, used toconcentrate acoustic ink jets EUP 572,220 sound waves. Sharp A sharppoint is used Simple Difficult to Tone-jet conductive to concentrate anconstruction fabricate using point electrostatic field. standard VLSIprocesses for a surface ejecting ink- jet Only relevant forelectrostatic ink jets ACTUATOR MOTION Volume The volume of the SimpleHigh energy is Hewlett-Packard expansion actuator changes, constructionin the typically required to Thermal Ink jet pushing the ink in all caseof thermal ink achieve volume Canon Bubblejet directions. jet expansion.This leads to thermal stress, cavitation, and kogation in thermal inkjet implementations Linear, The actuator moves in Efficient Highfabrication IJ01, IJ02, IJ04, normal to a direction normal to couplingto ink complexity may be IJ07, IJ11, IJ14 chip surface the print headsurface. drops ejected required to achieve The nozzle is typicallynormal to the perpendicular in the line of surface motion movement.Parallel to The actuator moves Suitable for Fabrication IJ12, IJ13,IJ15, chip surface parallel to the print planar fabrication complexityIJ33, IJ34, IJ35, head surface. Drop Friction IJ36 ejection may still beStiction normal to the surface. Membrane An actuator with a Theeffective Fabrication 1982 Howkins push high force but small area of theactuator complexity U.S. Pat. No. 4,459,601 area is used to push abecomes the Actuator size stiff membrane that is membrane areaDifficulty of in contact with the ink. integration in a VLSI processRotary The actuator causes Rotary levers Device IJ05, IJ08, IJ13, therotation of some may be used to complexity IJ28 element, such a grill orincrease travel May have impeller Small chip area friction at a pivotrequirements point Bend The actuator bends A very small Requires the1970 Kyser et al when energized. This change in actuator to be made U.S.Pat. No. 3,946,398 may be due to dimensions can be from at least two1973 Stemme differential thermal converted to a large distinct layers,or to U.S. Pat. No. 3,747,120 expansion, motion. have a thermal IJ03,IJ09, IJ10, piezoelectric difference across the IJ19, IJ23, IJ24,expansion, actuator IJ25, IJ29, IJ30, magnetostriction, or IJ31, IJ33,IJ34, other form of relative IJ35 dimensional change. Swivel Theactuator swivels Allows operation Inefficient IJ06 around a centralpivot. where the net linear coupling to the ink This motion is suitableforce on the paddle motion where there are is zero opposite forces Smallchip area applied to opposite requirements sides of the paddle, e.g.Lorenz force. Straighten The actuator is Can bs used with Requirescareful IJ26, IJ32 normally bent, and shape memory balance of stressesstraightens when alloys where the to ensure that the energized. austenicphase is quiescent bend is planar accurate Double The actuator bends inOne actuator can Difficult to make IJ36, IJ37, IJ38 bend one directionwhen be used to power the drops ejected by one element is two nozzles.both bend directions energized, and bends Reduced chip identical. theother way when size. A small another element is Not sensitive toefficiency loss energized. ambient temperature compared to equivalentsingle bend actuators. Shear Energizing the Can increase the Not readily1985 Fishbeck actuator causes a shear effective travel of applicable toother U.S. Pat. No. 4,584,590 motion in the actuator piezoelectricactuator material. actuators mechanisms Radial constriction The actuatorsqueezes Relatively easy High force 1970 Zoltan U.S. Pat. No. an inkreservoir, to fabricate single required 3,683,212 forcing ink from anozzles from glass Inefficient constricted nozzle. tubing as Difficultto macroscopic integrate with VLSI structures processes Coil/uncoil Acoiled actuator Easy to fabricate Difficult to IJ17, IJ21, IJ34, uncoilsor coils more as a planar VLSI fabricate for non- IJ35 tightly. Themotion of process planar devices the free end of the Small area Poorout-of-plane actuator ejects the ink. required, therefore stiffness lowcost Bow The actuator bows (or Can increase the Maximum travel IJ16,IJ18, IJ27 buckles) in the middle speed of travel is constrained whenenergized. Mechanically High force rigid required Push-Pull Twoactuators control The structure is Not readily IJ18 a shutter. Oneactuator pinned at both ends, suitable for ink jets pulls the shutter,and so has a high out-of- which directly push the other pushes it. planerigidity the ink Curl A set of actuators curl Good fluid flow DesignIJ20, IJ42 inwards inwards to reduce the to the region behind complexityvolume of ink that the actuator they enclose. increases efficiency CurlA set of actuators curl Relatively simple Relatively large IJ43 outwardsoutwards, pressurizing construction chip area ink in a chambersurrounding the actuators, and expelling ink from a nozzle in thechamber. Iris Multiple vanes enclose High efficiency High fabricationIJ22 a volume of ink. These Small chip area complexity simultaneouslyrotate, Not suitable for reducing the volume pigmented inks between thevanes. Acoustic The actuator vibrates The actuator can Large area 1993Hadimioglu vibration at a high frequency. be physically distant requiredfor et al, EUP 550,192 from the ink efficient operation 1993 Elrod etal, at useful frequencies EUP 572,220 Acoustic coupling and crosstalkComplex drive circuitry Poor control of drop volume and position None Invarious ink jet No moving parts Various other Silverbrook, EP designsthe actuator tradeoffs are 0771 658 A2 and does not move, required torelated patent eliminate moving applications parts Tone-jet NOZZLEREFILL METHOD Surface This is the normal way Fabrication Low speedThermal ink jet tension that ink jets are simplicity Surface tensionPiezoelectric ink refilled. After the Operational force relatively jetactuator is energized, simplicity small compared to IJ01–IJ07,IJ10–IJ14, it typically returns actuator force IJ16, IJ20, rapidly toits normal Long refill time IJ22–IJ45 position. This rapid usuallydominates return sucks in air the total repetition through the nozzlerate opening. The ink surface tension at the nozzle then exerts a smallforce restoring the meniscus to a minimum area. This force refills thenozzle. Shuttered Ink to the nozzle High speed Requires IJ08, IJ13,IJ15, oscillating chamber is provided at Low actuator common ink IJ17,IJ18, IJ19, ink pressure a pressure that energy, as the pressureoscillator IJ21 oscillates at twice the actuator need only May not bedrop ejection open or close the suitable for frequency. When a shutter,instead of pigmented inks drop is to be ejected, ejecting the ink dropthe shutter is opened for 3 half cycles: drop ejection, actuator return,and refill. The shutter is then closed to prevent the nozzle chamberemptying during the next negative pressure cycle. Refill After the mainHigh speed, as Requires two IJ09 actuator actuator has ejected a thenozzle is independent drop a second (refill) actively refilled actuatorsper nozzle actuator is energized. The refill actuator pushes ink intothe nozzle chamber. The refill actuator returns slowly, to prevent itsreturn from emptying the chamber again. Positive ink The ink is held aslight High refill rate, Surface spill Silverbrook, EP pressure positivepressure. therefore a high must be prevented 0771 658 A2 and After theink drop is drop repetition rate Highly related patent ejected, thenozzle is possible hydrophobic print applications chamber fills quicklyhead surfaces are Alternative for:, as surface tension and requiredIJ01–IJ07, IJ10–IJ14, ink pressure both IJ16, IJ20, IJ22–IJ45 operate torefill the nozzle. METHOD OF RESTRICTING BACK-FLOW THROUGH INLET Longinlet The ink inlet channel Design simplicity Restricts refill Thermalink jet channel to the nozzle chamber Operational rate Piezoelectric inkis made long and simplicity May result in a jet relatively narrow,Reduces relatively large chip IJ42, IJ43 relying on viscous crosstalkarea drag to reduce inlet Only partially back-flow. effective Positiveink The ink is under a Drop selection Requires a Silverbrook, EPpressure positive pressure, so and separation method (such as a 0771 658A2 and that in the quiescent forces can be nozzle rim or related patentstate some of the ink reduced effective applications drop alreadyprotrudes Fast refill time hydrophobizing, or Possible from the nozzle.both) to prevent operation of the This reduces the flooding of thefollowing: IJ01–IJ07, pressure in the nozzle ejection surface ofIJ09–IJ12, chamber which is the print head. IJ14, IJ16, IJ20, requiredto eject a IJ22, IJ23–IJ34, certain volume of ink. IJ36–IJ41, IJ44 Thereduction in chamber pressure results in a reduction in ink pushed outthrough the inlet. Baffle One or more baffles The refill rate is DesignHP Thermal Ink are placed in the inlet not as restricted as complexityJet ink flow. When the the long inlet May increase Tektronix actuator isenergized, method. fabrication piezoelectric ink jet the rapid inkReduces complexity (e.g. movement creates crosstalk Tektronix hot melteddies which restrict Piezoelectric print the flow through the heads).inlet. The slower refill process is unrestricted, and does not result ineddies. Flexible flap In this method recently Significantly Notapplicable to Canon restricts disclosed by Canon, reduces back-flow mostink jet inlet the expanding actuator for edge-shooter configurations(bubble) pushes on a thermal ink jet Increased flexible flap thatdevices fabrication restricts the inlet. complexity Inelasticdeformation of polymer flap results in creep over extended use Inletfilter A filter is located Additional Restricts refill IJ04, IJ12, IJ24,between the ink inlet advantage of ink rate IJ27, IJ29, IJ30 and thenozzle filtration May result in chamber. The filter Ink filter may becomplex has a multitude of fabricated with no construction small holesor slots, additional process restricting ink flow. steps The filter alsoremoves particles which may block the nozzle. Small inlet The ink inletchannel Design simplicity Restricts refill IJ02, IJ37, IJ44 compared tothe nozzle chamber rate to nozzle has a substantially May result in asmaller cross section relatively large chip than that of the nozzle,area resulting in easier ink Only partially egress out of the effectivenozzle than out of the inlet. Inlet shutter A secondary actuatorIncreases speed Requires separate IJ09 controls the position of of theink-jet print refill actuator and a shutter, closing off head operationdrive circuit the ink inlet when the main actuator is energized. Theinlet is The method avoids the Back-flow Requires careful IJ01, IJ03,IJ05, located problem of inlet back- problem is design to minimize IJ06,IJ07, IJ10, behind the flow by arranging the eliminated the negativeIJ11, IJ14, IJ16, ink-pushing ink-pushing surface of pressure behind theIJ22, IJ23, IJ25, surface the actuator between paddle IJ28, IJ31, IJ32,the inlet and the IJ33, IJ34, IJ35, nozzle. IJ36, IJ39, IJ40, IJ41 Partof the The actuator and a Significant Small increase in IJ07, IJ20,IJ26, actuator wall of the ink reductions in back- fabrication IJ38moves to chamber are arranged flow can be complexity shut off the sothat the motion of achieved inlet the actuator closes off Compactdesigns the inlet. possible Nozzle In some configurations Ink back-flowNone related to Silverbrook, EP actuator of ink jet, there is no problemis ink back-flow on 0771 658 A2 and does not expansion or eliminatedactuation related patent result in ink movement of an applicationsback-flow actuator which may Valve-jet cause ink back-flow Tone-jetthrough the inlet. NOZZLE CLEARING METHOD Normal All of the nozzles areNo added May not be Most ink jet nozzle firing fired periodically,complexity on the sufficient to systems before the ink has a print headdisplace dried ink IJ01, IJ02, IJ03, chance to dry. When IJ04, IJ05,IJ06, not in use the nozzles IJ07, IJ09, IJ10, are sealed (capped) IJ11,IJ12, IJ14, against air. IJ16, IJ20, IJ22, The nozzle firing is IJ23,IJ24, IJ25, usually performed IJ26, IJ27, IJ28, during a special IJ29,IJ30, IJ31, clearing cycle, after IJ32, IJ33, IJ34, first moving theprint IJ36, IJ37, IJ38, head to a cleaning IJ39, IJ40,, IJ41, station.IJ42, IJ43, IJ44,, IJ45 Extra In systems which heat Can be highlyRequires higher Silverbrook, EP power to the ink, but do not boileffective if the drive voltage for 0771 658 A2 and ink heater it undernormal heater is adjacent to clearing related patent situations, nozzlethe nozzle May require applications clearing can be larger driveachieved by over- transistors powering the heater and boiling ink at thenozzle. Rapid The actuator is fired in Does not require EffectivenessMay be used succession rapid succession. In extra drive circuits dependswith: IJ01, IJ02, of actuator some configurations, on the print headsubstantially upon IJ03, IJ04, IJ05, pulses this may cause heat Can bereadily the configuration of IJ06, IJ07, IJ09, build-up at the nozzlecontrolled and the ink jet nozzle IJ10, IJ11, IJ14, which boils the ink,initiated by digital IJ16, IJ20, IJ22, clearing the nozzle. In logicIJ23, IJ24, IJ25, other situations, it may IJ27, IJ28, IJ29, causesufficient IJ30, IJ31, IJ32, vibrations to dislodge IJ33, IJ34, IJ36,clogged nozzles. IJ37, IJ38, IJ39, IJ40, IJ41, IJ42, IJ43, IJ44, IJ45Extra Where an actuator is A simple Not suitable May be used power tonot normally driven to solution where where there is a with: IJ03, IJ09,ink pushing the limit of its motion, applicable hard limit to IJ16,IJ20, IJ23, actuator nozzle clearing may be actuator movement IJ24,IJ25, IJ27, assisted by providing IJ29, IJ30, IJ31, an enhanced driveIJ32, IJ39, IJ40, signal to the actuator. IJ41, IJ42, IJ43, IJ44, IJ45Acoustic An ultrasonic wave is A high nozzle High IJ08, IJ13, IJ15,resonance applied to the ink clearing capability implementation costIJ17, IJ18, IJ19, chamber. This wave is can be achieved if system doesnot IJ21 of an appropriate May be already include an amplitude andimplemented at very acoustic actuator frequency to cause low cost insystems sufficient force at the which already nozzle to clear includeacoustic blockages. This is actuators easiest to achieve if theultrasonic wave is at a resonant frequency of the ink cavity. Nozzle Amicrofabricated Can clear Accurate Silverbrook, EP clearing plate ispushed against severely clogged mechanical 0771 658 A2 and plate thenozzles. The plate nozzles alignment is related patent has a post forevery required applications nozzle. A post moves Moving parts arethrough each nozzle, required displacing dried ink. There is risk ofdamage to the nozzles Accurate fabrication is required Ink The pressureof the ink May be effective Requires May be used pressure is temporarilywhere other pressure pump or with all IJ series ink pulse increased sothat ink methods cannot be other pressure jets streams from all of theused actuator nozzles. This may be Expensive used in conjunctionWasteful of ink with actuator energizing. Print head A flexible ‘blade’is Effective for Difficult to use if Many ink jet wiper wiped across theprint planar print head print head surface is systems head surface. Thesurfaces non-planar or very blade is usually Low cost fragile fabricatedfrom a Requires flexible polymer, e.g. mechanical parts rubber orsynthetic Blade can wear elastomer. out in high volume print systemsSeparate A separate heater is Can be effective Fabrication Can be usedwith ink boiling provided at the nozzle where other nozzle complexitymany IJ series ink heater although the normal clearing methods jets drope-ection cannot be used mechanism does not Can be require it. Theheaters implemented at no do not require additional cost in individualdrive some ink jet circuits, as many configurations nozzles can becleared simultaneously, and no imaging is required. NOZZLE PLATECONSTRUCTION Electro- A nozzle plate is Fabrication High Hewlett Packardformed separately fabricated simplicity temperatures and Thermal Ink jetnickel from electroformed pressures are nickel, and bonded to requiredto bond the print head chip. nozzle plate Minimum thickness constraintsDifferential thermal expansion Laser Individual nozzle No masks Eachhole must Canon Bubblejet ablated or holes are ablated by an required beindividually 1988 Sercel et drilled intense UV laser in a Can be quitefast formed al., SPIE, Vol. 998 polymer nozzle plate, which is Somecontrol Special Excimer Beam typically a polymer over nozzle profileequipment required Applications, pp. such as polyimide or is possibleSlow where there 76–83 polysulphone Equipment are many thousands 1993Watanabe required is relatively of nozzles per print et al., U.S. Pat.No. low cost head 5,208,604 May produce thin burrs at exit holes SiliconA separate nozzle High accuracy is Two part K. Bean, IEEE micro- plateis attainable construction Transactions on machined micromachined fromHigh cost Electron Devices, single crystal silicon, Requires Vol. ED-25,No. 10, and bonded to the precision alignment 1978, pp 1185–1195 printhead wafer. Nozzles may be Xerox 1990 clogged by adhesive Hawkins etal., U.S. Pat. No. 4,899,181 Glass Fine glass capillaries No expensiveVery small 1970 Zoltan U.S. Pat. No. capillaries are drawn from glassequipment required nozzle sizes are 3,683,212 tubing. This method Simpleto make difficult to form has been used for single nozzles Not suitedfor making individual mass production nozzles, but is difficult to usefor bulk manufacturing of print heads with thousands of nozzles.Monolithic, The nozzle plate is High accuracy Requires Silverbrook, EPsurface deposited as a layer (<1 μm) sacrificial layer 0771 658 A2 andmicro- using standard VLSI Monolithic under the nozzle related patentmachined deposition techniques. Low cost plate to form the applications.using VLSI Nozzles are etched in Existing nozzle chamber IJ01, IJ02,IJ04, lithographic the nozzle plate using processes can be Surface maybe IJ11, IJ12, IJ17, processes VLSI lithography and used fragile to thetouch IJ18, IJ20, IJ22, etching. IJ24, IJ27, IJ28, IJ29, IJ30, IJ31,IJ32, IJ33, IJ34, IJ36, IJ37, IJ38, IJ39, IJ40, IJ41, IJ42, IJ43, IJ44Monolithic, The nozzle plate is a High accuracy Requires long IJ03,IJ05, IJ06, etched buried etch stop in the (<1 μm) etch times IJ07,IJ08, IJ09, through wafer. Nozzle Monolithic Requires a IJ10, IJ13,IJ14, substrate chambers are etched in Low cost support wafer IJ15,IJ16, IJ19, the front of the wafer, No differential IJ21, IJ23, IJ25,and the wafer is expansion IJ26 thinned from the back side. Nozzles arethen etched in the etch stop layer. No nozzle Various methods have Nonozzles to Difficult to Ricoh 1995 plate been tried to eliminate becomeclogged control drop Sekiya et al U.S. Pat. No. the nozzles entirely, toposition accurately 5,412,413 prevent nozzle Crosstalk 1993 Hadimiogluclogging. These problems et al EUP 550,192 include thermal bubble 1993Elrod et al mechanisms and EUP 572,220 acoustic lens mechanisms TroughEach drop ejector has Reduced Drop firing IJ35 a trough throughmanufacturing direction is sensitive which a paddle moves. complexity towicking. There is no nozzle Monolithic plate. Nozzle slit Theelimination of No nozzles to Difficult to 1989 Saito et al instead ofnozzle holes and become clogged control drop U.S. Pat. No. 4,799,068individual replacement by a slit position accurately nozzlesencompassing many Crosstalk actuator positions problems reduces nozzleclogging, but increases crosstalk due to ink surface waves DROP EJECTIONDIRECTION Edge Ink flow is along the Simple Nozzles limited CanonBubblejet (‘edge surface of the chip, construction to edge 1979 Endo etal GB shooter’) and ink drops are No silicon High resolution patent2,007,162 ejected from the chip etching required is difficult Xeroxheater-in- edge. Good heat Fast color pit 1990 Hawkins et sinking viasubstrate printing requires al U.S. Pat. No. 4,899,181 Mechanically oneprint head per Tone-jet strong color Ease of chip handing Surface Inkflow is along the No bulk silicon Maximum ink Hewlett-Packard (‘roofsurface of the chip, etching required flow is severely TIJ 1982 Vaughtet shooter’) and ink drops are Silicon can make restricted al U.S. Pat.No. 4,490,728 ejected from the chip an effective heat IJ02, IJ11, IJ12,surface, normal to the sink IJ20, IJ22 plane of the chip. Mechanicalstrength Through Ink flow is through the High ink flow Requires bulkSilverbrook, EP chip, chip, and ink drops are Suitable for siliconetching 0771 658 A2 and forward ejected from the front pagewidth printrelated patent (‘up surface of the chip. heads applications shooter’)High nozzle IJ04, IJ17, IJ18, packing density IJ24, IJ27–IJ45 thereforelow manufacturing cost Through Ink flow is through the High ink flowRequires wafer IJ01, IJ03, IJ05, chip, chip, and ink drops are Suitablefor thinning IJ06, IJ07, IJ08, reverse ejected from the rear pagewidthprint Requires special IJ09, IJ10, IJ13, (‘down surface of the chip.heads handling during IJ14, IJ15, IJ16, shooter’) High nozzlemanufacture IJ19, IJ21, IJ23, packing density IJ25, IJ26 therefore lowmanufacturing cost Through Ink flow is through the Suitable forPagewidth print Epson Stylus actuator actuator, which is notpiezoelectric print heads require Tektronix hot fabricated as part ofheads several thousand melt piezoelectric the same substrate asconnections to drive ink jets the drive transistors. circuits Cannot bemanufactured in standard CMOS fabs Complex assembly required INK TYPEAqueous, Water based ink which Environmentally Slow drying Most existingink dye typically contains: friendly Corrosive jets water, dye,surfactant, No odor Bleeds on paper All IJ series ink humectant, and Mayjets biocide. strikethrough Silverbrook, EP Modern ink dyes have Cocklespaper 0771 658 A2 and high water-fastness, related patent light fastnessapplications Aqueous, Water based ink which Environmentally Slow dryingIJ02, IJ04, IJ21, pigment typically contains: friendly Corrosive IJ26,IJ27, IJ30 water, pigment, No odor Pigment may Silverbrook, EPsurfactant, humectant, Reduced bleed clog nozzles 0771 658 A2 and andbiocide. Reduced wicking Pigment may related patent Pigments have anReduced clog actuator applications advantage in reduced strikethroughmechanisms Piezoelectric ink- bleed, wicking and Cockles paper jetsstrikethrough. Thermal ink jets (with significant restrictions) MethylMEK is a highly Very fast drying Odorous All IJ series ink Ethylvolatile solvent used Prints on various Flammable jets Ketone forindustrial printing substrates such as (MEK) on difficult surfacesmetals and plastics such as aluminum cans. Alcohol Alcohol based inksFast drying Slight odor All IJ series ink (ethanol, 2- can be used wherethe Operates at sub- Flammable jets butanol, printer must operate atfreezing and others) temperatures below temperatures the freezing pointof Reduced paper water. An example of cockle this is in-camera Low costconsumer photographic printing. Phase The ink is solid at No dryingtime- High viscosity Tektronix hot change room temperature, and inkinstantly freezes Printed ink melt piezoelectric (hot melt) is melted inthe print on the print medium typically has a ink jets head beforejetting. Almost any print ‘waxy’ feel 1989 Nowak Hot melt inks aremedium can be used Printed pages U.S. Pat. No. 4,820,346 usually waxbased, No paper cockle may ‘block’ All IJ series ink with a meltingpoint occurs Ink temperature jets around 80° C. After No wicking may beabove the jetting the ink freezes occurs curie point of almost instantlyupon No bleed occurs permanent magnets contacting the print Nostrikethrough Ink heaters medium or a transfer occurs consume powerroller. Long warm-up time Oil Oil based inks are High solubility Highviscosity: All IJ series ink extensively used in medium for some this isa significant jets offset printing. They dyes limitation for use in haveadvantages in Does not cockle ink jets, which improved paper usuallyrequire a characteristics on Does not wick low viscosity. Some paper(especially no through paper short chain and wicking or cockle).multi-branched oils Oil soluble dies and have a sufficiently pigmentsare required. low viscosity. Slow drying Microemulsion A microemulsionis a Stops ink bleed Viscosity higher All IJ series ink stable, selfforming High dye than water jets emulsion of oil, water, solubility Costis slightly and surfactant. The Water, oil, and higher than watercharacteristic drop size amphiphilic soluble based ink is less than 100nm, dies can be used High surfactant and is determined by Can stabilizeconcentration the preferred curvature pigment required (around of thesurfactant. suspensions 5%)

1. A printhead nozzle arrangement which comprises a substrate; drivecircuitry positioned on the substrate; a nozzle chamber structurearranged on the substrate, defining a nozzle chamber in fluidcommunication with a supply of ink and an ink ejection port in fluidcommunication with the nozzle chamber; and an actuator that is connectedto the drive circuitry and is operatively positioned with respect to thenozzle chamber, the actuator being reciprocally deformable between aquiescent condition and an active condition to eject ink from the inkejection port, wherein the actuator comprises a shape memory alloysandwiched between a first structural layer and a second structurallayer, the second structural layer being mechanically locked to thefirst structural layer to provide a stress reference for the firststructural layer, and wherein the shape memory alloy is in apre-stressed martensitic phase when the actuator is in the quiescentcondition and in an austenitic phase when the actuator is in the activecondition, such that cyclic phase changes generate said reciprocalmovement.
 2. A printhead nozzle arrangement as claimed in claim 1, inwhich the nozzle chamber structure is defined by an etched passagethrough the substrate, and an etch stop layer that defines the inkejection port.
 3. A printhead nozzle arrangement as claimed in claim 2,in which the substrate is of silicon, while the etch stop layer is aboron-doped epitaxial layer.
 4. A printhead nozzle arrangement asclaimed in claim 2, in which the actuator is positioned on thesubstrate, opposite the ink ejection port, the actuator being bent awayfrom the ink ejection port in the quiescent condition and straightenedtowards the ink ejection port in the active condition.
 5. A printheadnozzle arrangement as claimed in claim 4, in which the shape memoryalloy defines a heating circuit of the actuator, the heating circuithaving a substantially flat martensitic phase and being connected to thedrive circuitry to receive an electrical heating signal from the drivecircuitry, and a first structural layer that is positioned on theheating circuit, the first structural layer being the result of ahigh-temperature deposition so that, subsequent to cooling, the firststructural layer and the heating circuit bent into the quiescentcondition with the heating circuit in the martensitic phase.
 6. Aprinthead nozzle arrangement as claimed in claim 1, in which the firststructural layer is silicon nitride, the shape memory alloy is a nickeltitanium alloy and the second structural layer is silicon oxide.